Lens assembly

ABSTRACT

Examples of the disclosure enable a mobile device to generate high quality images. In some examples, the mobile device includes a lens assembly that includes a first lens configured to provide positive optical power, and a telephoto stage including a second lens configured to provide negative optical power, and a third lens configured to perform one or more of increasing a sharpness and decreasing a distortion of an image associated with light transmitted through the lens assembly. The lens assembly has a track length that is less than or equal to approximately 6.0 mm and a focal length that is greater than or equal to approximately 7.3 mm. Aspects enable a lens assembly to be used in a mobile device environment, such that a mobile device including and/or associated with the lens assembly is configured to take high quality images.

BACKGROUND

Mobile devices, such as laptops, smartphones, tablets, and/or phablets,are increasingly used to take pictures. At least some pictures takenwith known mobile devices are suitable for personal use (e.g., keepsakepictures). However, at least some mobile devices are restricted bycurrent infrastructure (e.g., size requirements, hardware requirements)to take pictures suitable for other purposes, such as biometricidentification, medical and diagnostic images, and/or machine vision.For example, at least some pictures for such purposes taken with knownmobile devices have relatively low resolution, are out of focus, areblurry, and/or are not crisp when compared to pictures taken withdedicated systems, which are not constrained to a mobile deviceenvironment.

SUMMARY

Examples of the disclosure enable a mobile device to take high qualitypictures suitable for purposes such as biometric identification, medicaland diagnostic images, and/or machine vision. Some examples include alens assembly including a first lens configured to provide positiveoptical power, and a telephoto stage including a second lens configuredto provide negative optical power, and a third lens configured toperform increasing a sharpness and/or decreasing a distortion of animage associated with light transmitted through the lens assembly. Inthis example, the lens assembly has a track length that enables the lensassembly to fit within the mobile device (e.g., less than or equal toapproximately 6.0 mm) and a focal length that enables the lens assemblyto generate an image having a desired image resolution (e.g., greaterthan or equal to approximately 7.3 mm).

This Summary is provided to introduce a selection of concepts in asimplified form that are further described below in the DetailedDescription. This Summary is not intended to identify key features oressential features of the claimed subject matter, nor is it intended tobe used as an aid in determining the scope of the claimed subjectmatter.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of an example mobile device.

FIG. 2 is a schematic illustration of a sensor module that may be usedwith a mobile device, such as the mobile device shown in FIG. 1.

FIG. 3 is a plan view of an example lens assembly that may be used witha sensor module, such as the sensor module shown in FIG. 2.

FIG. 4 is a schematic illustration of an example implementation of alens assembly, such as the lens assembly shown in FIG. 3.

FIG. 5 is a schematic illustration of another example implementation ofa lens assembly, such as the lens assembly shown in FIG. 3.

FIG. 6 is a flow chart illustrating an example method of collectinglight using a sensor module, such as the sensor module shown in FIG. 2.

Corresponding reference characters indicate corresponding partsthroughout the drawings.

DETAILED DESCRIPTION

Examples of the disclosure enable a mobile device to take high qualitypictures for sensitive use, such as biometric identification, medicaland diagnostic images, and/or machine vision. Some examples include alens assembly including a first lens configured to provide a positiveoptical power, and a telephoto stage including a second lens configuredto provide a negative optical power, and a third lens configured toincrease a sharpness and/or decrease a distortion of an image associatedwith light transmitted through the lens assembly. In this example, thelens assembly has a track length that is less than or equal toapproximately 6.0 mm and a focal length that is greater than or equal toapproximately 7.3 mm.

Aspects of the disclosure enable a lens assembly to be used in a mobiledevice environment, such that a mobile device including and/orassociated with the lens assembly is configured to take high qualitypictures. For example, the lens assembly described herein enablesrelatively-high image quality specifications to be satisfied bygenerating images having adequate resolution, magnification, minimaldistortion, etc. By incorporating the lens assembly in the mannerdescribed in this disclosure, some examples enable miniaturization,e.g., require less space for functionality, improved usability, and/orenhanced reliability of a device.

FIG. 1 is a block diagram of an example environment 100 including amobile device 110. In some examples, the mobile device 110 may be and/orinclude a laptop, a smartphone, a tablet, a phablet, a mobile telephone,a portable media player, a netbook, a computing pad, a desktop computer,a set-top box, a game console, a kiosk, a tabletop device, and/or anyother computing device. While some examples of the disclosure areillustrated and described herein with reference to a mobile device 110,aspects of the disclosure are operable with any computing device thatexecutes instructions to implement the operations and functionalityassociated with the computing device.

In this example, the mobile device 110 includes one or morecomputer-readable media, such as a memory area 120 storingcomputer-executable instructions, biometric data, medical and diagnosticimages, machine data, and/or other data, and one or more processors 130programmed to execute the computer-executable instructions forimplementing aspects of the disclosure. The memory area 120 includes anyquantity of media associated with or accessible by the computing device.The memory area 120 may be internal to the computing device (as shown inFIG. 1), external to the computing device (not shown), or both (notshown).

In some examples, the memory area 120 stores, among other data, one ormore applications. The applications, when executed by the processor 130,operate to perform a functionality on the mobile device 110. Exampleapplications include a mail application program, a web browser, acalendar application program, an address book application program, amessaging program, a media program, a location-based service program, asearch program, and the like. The applications may communicate withcounterpart applications or services, such as web services accessiblevia a network (not shown). For example, the applications may representdownloaded client-side applications that correspond to server-sideservices executing in the cloud.

The processor 130 includes any quantity of processing units, and theinstructions may be performed by the processor 130 or by multipleprocessors within the computing device or performed by a processorexternal to the computing device. In some examples, the processor 130 istransformed into a special purpose microprocessor by executingcomputer-executable instructions or by otherwise being programmed.Although the processor 130 is shown separate from the memory area 120,examples of the disclosure contemplate that the memory area 120 may beonboard the processor 130 such as in some embedded systems.

In some examples, the mobile device 110 includes one or more userinterfaces 140 for exchanging data between the mobile device 110 and auser 150. For example, the user interface 140 includes and/or is coupledto a presentation device configured to present information, such astext, images, audio, video, graphics, alerts, and the like, to the user150. The presentation device may include, without limitation, a display,a speaker, and/or a vibrating component. Additionally or alternatively,the user interface 140 includes and/or is coupled to an input device(not shown) configured to receive information, such as user commands,from the user 150. The input device may include, without limitation, acontroller, a camera, a microphone, and/or an accelerometer. In at leastsome examples, the presentation device and the input device areintegrated in a common user interface 140 configured to presentinformation to the user 150 and receive information from the user 150.For example, the user-interface device may include, without limitation,a capacitive touch screen display and/or a controller including avibrating component.

In this example, a user interface 140 includes and/or is coupled to atleast one sensor module 160. For example, the sensor module 160 mayinclude a circuit board (not shown) and an image sensor (shown, e.g., inFIG. 2) coupled to the circuit board. In at least some examples, theimage sensor is a complementary metal-oxide semiconductor (CMOS) and/orchard-coupled device (CCD) image sensor. Alternatively, the image sensormay be any type of sensor that enables the mobile device 110 to functionas described herein.

In some examples, the mobile device 110 includes at least onecommunication interface 170 for exchanging data between the mobiledevice 110 and a computer-readable media and/or another computingdevice. Communication between the mobile device 110 and acomputer-readable media and/or another computing device may occur usingany protocol or mechanism over any wired or wireless connection. Forexample, the mobile device 110 may communicate with a computer-readablemedia and/or another computing device using a BLUETOOTH brand wirelesstechnology standard, using a WI-FI brand wireless technology standard(e.g., IEEE 802.11), and/or via a cellular network (e.g., 3G, 4G).(BLUETOOTH is a trademark of Bluetooth Special Interest Group; WI-FI isa trademark of the Wi-Fi Alliance).

The block diagram of FIG. 1 is merely illustrative of an exampleenvironment that may be used in connection with one or more examples ofthe disclosure and is not intended to be limiting in any way. Further,peripherals or components of the computing devices known in the art arenot shown, but are operable with aspects of the disclosure. At least aportion of the functionality of the various elements in FIG. 1 may beperformed by other elements in FIG. 1, or an entity (e.g., processor,web service, server, applications, computing device, etc.) not shown inFIG. 1.

FIG. 2 is a perspective view of the sensor module 160. In some examples,the sensor module 160 includes a barrel and/or housing 200 that at leastpartially defines a cavity 202 configured to house a plurality ofoptical components arranged along an optical axis 204. In this example,the housing 200 has an inner surface 206 that defines an aperture 208.The aperture 208 is sized, shaped, and/or configured to allow light(e.g., one or more light rays) to enter the cavity 202. In this example,the housing 200 houses an image sensor 210 and a lens assembly 220within the cavity 202. FIG. 3 is a plan view of the lens assembly 220.The image sensor 210 may be any suitable type of image sensor including,without limitation, a CMOS sensor and/or a CCD sensor.

In some examples, the sensor module 160 includes a filter 230 (e.g.,band-pass filter, infrared filter) configured to allow or pass at leasta first light (e.g., visible light) through the filter 230 and/or blockor restrict at least a second light (e.g., infrared light) from passingthrough the filter 230. In this example, the filter 230 is positionedadjacent the image sensor 210 along the optical axis 204 to filter atleast some light at a location proximate to the image sensor 210.Alternatively, the filter 230 may be positioned at any location thatenables the sensor module 160 to function as described herein.

The lens assembly 220 is configured to capture light, and bend thecaptured light into a flat field of focus on the image sensor 210. In atleast some examples, the image is suitable for various purposes, such asbiometric identification, medical and diagnostic images, and/or machinevision. In some examples, the lens assembly 220 includes a first stage240 and a second stage 250. Alternatively, the lens assembly 220 mayinclude any number of stages that enables the lens assembly 220 tofunction as described herein.

The lens assembly 220 is configured to function in a predeterminedspectrum of light. For example, the lens assembly 220 may be configuredto function in a band of infrared light (e.g., approximately 700nm-approximately 1000 nm). In this disclosure, unless otherwise stated,adjectives such as “approximately”, “substantially”, and “about”modifying a condition or relationship characteristic of a feature orfeatures of an embodiment of the disclosure are understood to mean thatthe condition or characteristic is defined to within tolerances that areacceptable for operation of the embodiment for an application for whichit is intended. Infrared light may be desired for at least some irisimaging operations. In one example, the lens assembly 220 is configuredto function in a spectrum of near-infrared light of a light emittingdiode (LED) light source (e.g., approximately 830 nm-approximately 870nm). Additionally or alternatively, the lens assembly 220 may beconfigured to function as described herein in at least a portion of avisible light wavelength band (e.g., approximately 400 nm-approximately700 nm). Shorter wavelengths may be desired for at least some relativelyhigh resolution operations. The lens assembly 220 may be configured tofunction with any spectrum of light that enables the lens assembly 220to function as described herein.

In some examples, the first stage 240 includes a first lens 260positioned at and/or proximate to a front of the lens assembly 220 alongthe optical axis 204. In this example, the first lens 260 is within theaperture 208. Alternatively, the first lens 260 may be at any locationthat enables the lens assembly 220 to function as described herein. Asused herein, the term “front” refers to a position that is proximate tothe aperture 208, and the term “rear” refers to a position that isproximate to the image sensor 210. While a single lens is shown for eachlens (e.g., first lens 260), it will be understood that, in otherexamples, each lens may include a plurality of lenses that, whencombined, have the respective optical characteristics described hereinfor each lens and that the term “lens” as used herein may also refer tosuch plural lens arrangement.

The first lens 260 is configured to provide a high positive opticalpower. In this example, the first lens 260 is a positive, generallymeniscus lens having a relatively-steep convex front surface 262 and arelatively-gentle concave rear surface 264 (shown in FIG. 2) such that athickness 266 (shown in FIG. 2) of the first lens 260 (e.g., distancebetween the front surface 262 and the rear surface 264) is thicker at aninner portion 268 than at an outer portion 270. In this example, thefirst lens 260 is an aspheric lens, and the front surface 262 and/or therear surface 264 are aspheric surfaces.

The first lens 260 is configured to bend incoming light towards a firstfocal point 272 (shown in FIG. 2). In this example, the first lens 260is a stronger positive lens than the other lens in the lens assembly220. The first lens 260 is configured to bend light across a desiredfield of view such that an amount of light at a position proximate to anedge of the field of view is comparable with the amount of light at aposition proximate to the center of the field of view. The field of viewprovides a desired coverage of an area that allows imaging of one orboth eyes of a user. The first lens 260 is configured to bend light forthe desired field of view with little to no distortion and such thatsharpness is ensured across a desired field of view. The first lens 260enables the lens assembly 220 to have a track length such that the lensassembly 220 may be housed within a mobile device 110 and/or housing200. In at least some examples, the first lens 260 enables the tracklength (e.g., a total track length) to be less than or equal toapproximately 6.0 mm. Alternatively, the track length may be anydistance that enables the lens assembly 220 to be used in a mobiledevice environment 100. While the first stage 240 is shown including asingle lens (e.g., first lens 260), it will be understood that, in otherexamples, the first stage 240 may include a plurality of lenses that,when combined, have the optical characteristics described herein for thefirst stage 240.

In some examples, the second stage 250 is a telephoto stage that isconfigured to provide negative optical power. In this example, thesecond stage 250 enables the lens assembly 220 to have a focal lengththat is greater than or equal to the track length. The second stage 250is configured to bend light such that an image generated from the lightemitted from the second stage 250 may have a desired resolution for atleast some applications (e.g., iris detection, iris imaging). Forexample, an image resolution of approximately 160-200 pixels per irismay be desired for iris recognition applications. To generate an imagehaving an image having an image resolution of approximately 160-200pixels per iris, in this example, the lens assembly 220 has a focallength of approximately 7.3 mm for near-infrared light.

In some examples, the second stage 250 includes a second lens 274positioned behind the first lens 260 along the optical axis 204. In thisexample, the second lens 274 is positioned within the cavity 202.Alternatively, the second lens 274 may be at any location that enablesthe lens assembly 220 to function as described herein.

The second lens 274 is configured to provide a negative optical power.In this example, the second lens 274 is a negative, generally biconcavelens having a relatively-gentle concave front surface 276 (shown in FIG.2) and a relatively-steep concave rear surface 278 (shown in FIG. 2)such that a thickness 280 (shown in FIG. 2) of the second lens 274(e.g., distance between the front surface 276 and the rear surface 278)is thinner at an inner portion 282 than at an outer portion 284. In thisexample, the second lens 274 is an aspheric lens, and the front surface276 and/or the rear surface 278 are aspheric surfaces.

The second lens 274 is a telephoto lens configured to bend incominglight towards a second focal point 286 (shown in FIG. 2) farther backthan the first focal point 272 (e.g., farther from the aperture 208and/or first lens 260). The second lens 274 is configured to bend lightacross a desired field of view such that an amount of light at aposition proximate to an edge of the field of view is comparable withthe amount of light at a position proximate to the center of the fieldof view. The field of view provides a desired coverage of an area thatallows imaging of one or both eyes of a user. The second lens 274 isconfigured to bend light for the desired field of view with little to nodistortion and such that sharpness is ensured across a desired field ofview. In at least some examples, the second lens 274 is configured toadjust, correct, and/or limit an effect of chromatic aberration. Forexample, the second lens 274 may be fabricated from a lens material,such as polycarbonate, acrylic, and/or polystyrene that enables thesecond lens 274 to adjust, correct, and/or limit an effect of chromaticaberration. Alternatively, the second lens 274 may be fabricated fromany material that enables the lens assembly 220 to function as describedherein.

In some examples, the second stage 250 includes a third lens 288positioned behind the second lens 274 along the optical axis 204. Inthis example, the third lens 288 is positioned within the cavity 202.Alternatively, the third lens 288 may be at any location that enablesthe lens assembly 220 to function as described herein.

In some examples, the third lens 288 is configured to provide a positiveor a negative optical power. In this example, the third lens 288 is apositive, generally meniscus lens having a relatively-gentle concavefront surface 290 (shown in FIG. 2) and a relatively-steep convex rearsurface 292 such that a thickness 294 (shown in FIG. 2) of the thirdlens 288 (e.g., distance between the front surface 290 and the rearsurface 292) is thicker at an inner portion 296 than at an outer portion298. In this example, the third lens 288 is an aspheric lens, and thefront surface 290 and/or the rear surface 292 are aspheric surfaces.

In some examples, the third lens 288 is configured to increase asharpness and/or reduce a distortion and/or field curvature of an imageon the image sensor 210. In at least some examples, the third lens 288is configured to bend incoming light based on a distance from theoptical axis 204. For example, a light ray transmitted through the innerportion 296 is bent to a lesser degree than a light ray transmittedthrough the outer portion 298 and/or a light ray transmitted through theouter portion 298 is bent to a greater degree than a light raytransmitted through the inner portion 296. The third lens 288 isconfigured to bend light across a desired field of view such that anamount of light at a position proximate to an edge of the field of viewis comparable with the amount of light at a position proximate to thecenter of the field of view. The field of view provides a desiredcoverage of an area that allows imaging of one or both eyes of a user.The third lens 288 is configured to bend light for the desired field ofview with little to no distortion and such that sharpness is ensuredacross a desired field of view. Accordingly, in this example, the innerportion 296 is configured to adjust, correct, and/or limit the fieldcurvature to a first extent, and the outer portion 298 is configured toadjust, correct, and/or limit the field curvature to a second extentgreater than the first extent.

In this example, the third lens 288 is positioned such that the lensassembly 220 has a back focal length (e.g., distance between the rearsurface 292 of the third lens 288 the focal point on the image sensor210) is greater than or equal to approximately 1.0 mm. The back focallength allows for focal adjustment and/or use of one or more filters 230in front of the image sensor 210. While the second stage 250 is shownincluding two lenses (e.g., second lens 274 and third lens 288), it willbe understood that, in other examples, the second stage 250 may includea plurality of lenses that, when combined, have the opticalcharacteristics described herein for the second stage 250.

The first lens 260, second lens 274, and/or third lens 288 may beconstructed in any suitable manner. For example, the first lens 260,second lens 274, and/or third lens 288 may be fabricated from a plasticmaterial and/or a glass material. Plastic materials may help reducematerial and/or manufacturing costs, and glass materials may helpimprove thermal stability. The materials of the first lens 260, secondlens 274, and/or third lens 288 may be different from one another inorder to adjust, correct, and/or limit color, reduce field of curvatureand distortion, etc. In this example, each of the first lens 260, secondlens 274, and third lens 288 includes a plurality of aspheric surfacesto adjust, correct, and/or limit for rays falling on the peripherals ofthe lens surfaces. This may help to reduce optical aberrations, therebyhelping to open up the aperture size of the housing 200.

FIG. 4 is a schematic illustration of one implementation of the lensassembly 220. In this example, the lens assembly 220 is configured foruse with an image sensor 210 configured to generate one or more imageshaving a pixel size of approximately 1.4 microns square. FIG. 4illustrates how various light rays 400 traverse through the lensassembly 220. In some examples, the lens assembly 220 is configured toenable a Modulation Transfer Function (MTF) value greater than or equalto approximately 0.15 (e.g., 15%) to be achieved at approximately 357line pairs per millimeter (lp/mm), which would provide a pixelresolution of approximately 1.4 micron when imaging an object (e.g., aniris) at approximately 400 mm across a field of view of approximately 22degrees. In at least some examples, the lens assembly 220 enables an MTFof greater than or equal to approximately 0.60 (e.g., 60%) to beachieved at approximately 178 lp/mm across a field of view ofapproximately 22 degrees. The lens assembly 220 also produces less thanor equal to approximately 2% of distortion and greater than or equal toapproximately 90% illumination uniformity across a field of view ofapproximately 22 degrees.

FIG. 5 is a schematic illustration of another implementation of the lensassembly 220. In this example, the lens assembly 220 is configured foruse with image sensor 210 configured to generate one or more imageshaving a pixel size of approximately 1.1 microns square. FIG. 5illustrates how various light rays 500 traverse through the lensassembly 220. The smaller pixel size enables a higher-resolution image(e.g., an image resolution greater than approximately 200 pixels periris for a working distance or approximately 400 mm) to be generatedand/or the track length to be shortened (e.g., shorter than 6 mm). Inthese implementations, the lens assembly 220 enables at least apredetermined number of pixels (e.g., approximately 160-200 pixels periris) that provide reliable and/or robust data to cover an iris of auser (e.g., user 150).

FIG. 6 is a flow chart illustrating an example method 600 of collectinglight using a sensor module 160. The method 600 includes, at 610, usinga first lens 260 configured to provide positive optical power to collectlight from a light source, bend the light rays, and direct the lightrays towards a first focal point 272. At 620, a second lens configuredto provide negative optical power is used to collect light rays from thefirst lens 260, bend light rays toward a second focal point 286 a seconddistance farther from the first lens 260 than the first distance, and/oradjust an effect of chromatic aberration. At 630, a third lens 288 isused to collect light rays from the second lens 274, bend light rays toincrease sharpness and/or reduce distortion, and direct light raystowards an image sensor 210. For example, one or more first light raystraversing an inner portion 296 of the third lens 288 are corrected to afirst extent, and one or more second light rays traversing an outerportion 298 of the third lens 288 are corrected to a second extentgreater than the first extent. In at least some examples, a filter 230is used at 640 to pass a first light ray (e.g., visible light) throughtowards the image sensor 210 and/or block a second light ray (e.g.,infrared light) from passing through the filter 230.

The subject matter described herein enables a mobile device to generatehigh quality images suitable for a variety of applications. In someexamples, a lens assembly housed within a mobile device has a focallength that enables the lens assembly to generate one or more imagesthat satisfy image quality specifications for iris recognitionapplications. For example, the lens assembly provides a desiredresolution, magnification, distortion, etc. In this way, the mobiledevice may be used to generate high quality images while maintaining alow profile.

Although described in connection with an example computing systemenvironment, examples of the disclosure are capable of implementationwith numerous other general purpose or special purpose computing systemenvironments, configurations, or devices.

Examples of well-known computing systems, environments, and/orconfigurations that may be suitable for use with aspects of thedisclosure include, but are not limited to, mobile computing devices,personal computers, server computers, hand-held or laptop devices,multiprocessor systems, gaming consoles, microprocessor-based systems,set top boxes, programmable consumer electronics, mobile telephones,mobile computing and/or communication devices in wearable or accessoryform factors (e.g., watches, glasses, headsets, or earphones), networkPCs, minicomputers, mainframe computers, distributed computingenvironments that include any of the above systems or devices, and thelike. Such systems or devices may accept input from the user in any way,including from input devices such as a keyboard or pointing device, viagesture input, proximity input (such as by hovering), and/or via voiceinput.

The examples illustrated and described herein as well as examples notspecifically described herein but within the scope of aspects of thedisclosure constitute example means for bending light rays towards afirst focal point, example means for bending light rays towards a secondfocal point, and/or example means for directing light rays toward asensor module.

The order of execution or performance of the operations in examples ofthe disclosure illustrated and described herein is not essential, unlessotherwise specified. That is, the operations may be performed in anyorder, unless otherwise specified, and examples of the disclosure mayinclude additional or fewer operations than those disclosed herein. Forexample, it is contemplated that executing or performing a particularoperation before, contemporaneously with, or after another operation iswithin the scope of aspects of the disclosure.

When introducing elements of aspects of the disclosure or the examplesthereof, the articles “a,” “an,” “the,” and “said” are intended to meanthat there are one or more of the elements. The terms “comprising,”‘including,” and “having” are intended to be inclusive and mean thatthere may be additional elements other than the listed elements. Thephrase “one or more of the following: A, B, and C” means “at least oneof A and/or at least one of B and/or at least one of C.”

Having described aspects of the disclosure in detail, it will beapparent that modifications and variations are possible withoutdeparting from the scope of aspects of the disclosure as defined in theappended claims. As various changes could be made in the aboveconstructions, products, and methods without departing from the scope ofaspects of the disclosure, it is intended that all matter contained inthe above description and shown in the accompanying drawings shall beinterpreted as illustrative and not in a limiting sense.

Alternatively or in addition to the other examples described herein,examples include any combination of the following:

a lens barrel including a housing that at least partially defines acavity therein;

a lens barrel including an inner surface that defines an aperture;

a first lens configured to provide positive optical power;

a first lens having one or more aspheric surfaces;

a first lens within an aperture;

a telephoto stage including a second lens and a third lens;

a telephoto stage configured to provide negative optical power.

a second lens configured to provide negative optical power;

a second lens having one or more aspheric surfaces;

a second lens that is a telephoto lens;

a second lens configured to adjust a chromatic aberration of the image;

a second lens within a cavity;

a third lens configured to provide positive optical power;

a third lens configured to perform increasing a sharpness and/ordecreasing a distortion of an image;

a third lens configured to adjust a field curvature of the image;

a third lens including an inner portion configured to adjust the fieldcurvature to a first extent, and an outer portion configured to adjustthe field curvature to a second extent greater than the first extent;

a third lens having one or more aspheric surfaces;

a third lens within a cavity;

a lens assembly having a track length that is less than or equal toapproximately 6.0 mm;

a lens assembly having a track length that enables the lens assembly tobe positioned within the housing;

a lens assembly having a focal length that is greater than or equal toapproximately 7.3 mm;

a lens assembly having a focal length that is greater than or equal tothe track length;

a lens assembly having a back focal length greater than or equal toapproximately 1.0 mm;

bending, at a first lens having one or more aspheric surfaces, aplurality of light rays towards a first focal point a first distancefrom the first lens;

bending, at a second lens having one or more aspheric surfaces, aplurality of light rays towards a second focal point a second distancefarther from the first lens than the first distance;

directing, at a third lens having one or more aspheric surfaces, theplurality of light rays towards a sensor module such that the sensormodule is configured to generate an image based on the plurality oflight rays;

adjusting, at the second lens, a chromatic aberration of the image; and

adjusting, at the third lens, a field curvature of the image, whereinone or more first light rays traversing an inner portion of the thirdlens are adjusted to a first extent, and one or more second light raystraversing an outer portion of the third lens are adjusted to a secondextent greater than the first extent.

While the aspects of the disclosure have been described in terms ofvarious examples with their associated operations, a person skilled inthe art would appreciate that a combination of operations from anynumber of different examples is also within scope of the aspects of thedisclosure.

What is claimed is:
 1. A lens assembly comprising: a first lensconfigured to provide positive optical power; and a telephoto stagecomprising a second lens and a third lens, the second lens configured toprovide negative optical power, and the third lens configured to performone or more of increasing a sharpness or decreasing a distortion of animage associated with light transmitted through the lens assembly,wherein the first lens is a positive meniscus lens with a convex frontsurface and a concave rear surface, the second lens is a negativebiconcave lens with a concave front surface and a concave rear surface,a curvature of the concave rear surface of the second lens is greaterthan a curvature of the concave front surface of the second lens, andthe third lens is a positive meniscus lens with a concave front surfaceand a convex rear surface, and wherein the lens assembly has a backfocal length greater than or equal to approximately 1.0 mm.
 2. The lensassembly of claim 1, wherein the first lens has one or more asphericsurfaces, and wherein the first lens comprises a convex front surfaceand a concave rear surface such that a thickness of the first lens isthicker at an inner portion than at an outer portion of the first lens.3. The lens assembly of claim 1, wherein the telephoto stage isconfigured to provide negative optical power.
 4. The lens assembly ofclaim 1, wherein the second lens has one or more aspheric surfaces. 5.The lens assembly of claim 1, wherein the second lens is a telephotolens.
 6. The lens assembly of claim 1, wherein the second lens isconfigured to adjust a chromatic aberration of the image.
 7. The lensassembly of claim 1, wherein the third lens has one or more asphericsurfaces, and wherein the third lens comprises a concave front surfaceand a convex rear surface such that a thickness of the third lens isthicker at an inner portion than at an outer portion of the third lens,the lens assembly having a track length that enables the lens assemblyto fit within a mobile device and a focal length for near-infraredlight.
 8. The lens assembly of claim 1, wherein the third lens isconfigured to provide positive optical power.
 9. The lens assembly ofclaim 1, wherein the third lens is configured to adjust a fieldcurvature of the image, the third lens comprising an inner portionconfigured to adjust the field curvature to a first extent, and an outerportion configured to adjust the field curvature to a second extentgreater than the first extent.
 10. A mobile device comprising: a lensbarrel comprising a housing that at least partially defines a cavitytherein; an adjustable filter; and a lens assembly comprising: a firstlens configured to provide positive optical power, a second lensconfigured to provide negative optical power, and a third lensconfigured to perform one or more of increasing a sharpness ordecreasing a distortion of an image associated with light transmittedthrough the lens assembly, the second lens and the third lens positionedwithin the cavity, the lens assembly having a track length that enablesthe lens assembly to be positioned within the housing and a focal lengththat is greater than or equal to the track length, wherein the firstlens is a positive meniscus lens with a convex front surface and aconcave rear surface, the second lens is a negative biconcave lens witha concave front surface and a concave rear surface, a curvature of theconcave rear surface of the second lens is greater than a curvature ofthe concave front surface of the second lens, the third lens is apositive meniscus lens with a concave front surface and a convex rearsurface, and the adjustable filter is configured to allow at least afirst light ray and block or restrict at least a second light ray, andwherein the lens assembly has a back focal length greater than or equalto approximately 1.0 mm.
 11. The mobile device of claim 10, wherein thelens barrel includes an inner surface that defines an aperture, thefirst lens within the aperture.
 12. The mobile device of claim 10,wherein each of the first lens, the second lens, and the third lens hasa plurality of aspheric surfaces.
 13. The mobile device of claim 10,wherein the second lens is configured to adjust a chromatic aberrationof the image.
 14. The mobile device of claim 10, wherein the third lensis configured to provide positive optical power.
 15. The mobile deviceof claim 10, wherein the third lens is configured to adjust a fieldcurvature of the image, the third lens comprising an inner portionconfigured to adjust the field curvature to a first extent, and an outerportion configured to adjust the field curvature to a second extentgreater than the first extent.
 16. A method for collecting light using alens assembly, the method comprising: bending, at a first lens havingone or more aspheric surfaces, a plurality of light rays towards a firstfocal point a first distance from the first lens, the first lensconfigured to provide positive optical power, at least a portion of theplurality of light rays in a spectrum of near-infrared light of a lightemitting diode light source; bending, at a second lens having one ormore aspheric surfaces, the plurality of light rays towards a secondfocal point a second distance farther from the first lens than the firstdistance, the second lens configured to provide negative optical power;and directing, at a third lens having one or more aspheric surfaces, theplurality of light rays towards a sensor module such that the sensormodule is configured to generate an image based on the plurality oflight rays, the third lens configured to perform one or more ofincreasing a sharpness or decreasing a distortion of the image, the lensassembly having a track length that is less than or equal toapproximately 6.0 mm and a focal length that is greater than or equal toapproximately 7.3 mm, wherein the first lens is a positive meniscus lenswith a convex front surface and a concave rear surface, the second lensis a negative biconcave lens with a concave front surface and a concaverear surface, a curvature of the concave rear surface of the second lensis greater than a curvature of the concave front surface of the secondlens, and the third lens is a positive meniscus lens with a concavefront surface and a convex rear surface, and wherein the lens assemblyhas a back focal length greater than or equal to approximately 1.0 mm.17. The method of claim 16, further comprising adjusting, at the secondlens, a chromatic aberration of the image.
 18. The method of claim 16,further comprising adjusting, at the third lens, a field curvature ofthe image, wherein one or more first light rays of the plurality oflight rays traversing an inner portion of the third lens are adjusted toa first extent, and one or more second light rays of the plurality oflight rays traversing an outer portion of the third lens are adjusted toa second extent, the second extent being greater than the first extent.19. The method of claim 16, wherein the second and the third lenscomprise a telephoto stage which is configured to provide negativeoptical power.
 20. The method of claim 16, wherein the second lens hasone or more aspheric surfaces.